In vivo panning with phage display libraries has proved to be a powerful method to identify novel vascular bed-specific peptide homing sequences. In this application we propose to study the binding characteristics of a newly identified prostate endothelial-specific sequence. The relative contribution of affinity and avidity will be studied by assessing the effect of peptide copy number on phage homing in vivo as well as binding affinity to cells isolated from the prostate in vitro. The critical amino acid residues within this prostate-specific heptapeptide sequence will be determined. We also propose to screen for additional prostate specific peptides by screening the CX3CX3C and CX6C phage display libraries, since these yield cyclic peptides that may exhibit higher binding affinities. By better understanding the binding requirements as well as the homing potential in normal compared to developing tumor tissue, these studies will provide essential fundamental information required to translate specific peptides identified with a multivalent phage display system into practical therapeutic or diagnostic tools for prostate hypertrophy and cancer. PROPOSED COMMERCIAL APPLICATION: NOT AVAILABLE